a box on page 19 of GURPS Psionic Powers
refers to going below -80% value in limitations
example given of 25 points reducing to 1 (1/25 is 4% so this is -96%) being applied from -140% total limitations.
it refers to page 42's perk Visions (Aspected Dream) which refers to page 39's Visions (Dream) and Visions (Aspected) both of which are derived from Precognition
An even more extreme example is the 100-point advantage of Warp being reduced to a perk, which is -99%. This is called Castling on PP69.